Extended pitch saw chain

ABSTRACT

A cutter link for a saw chain including an elongated base having front and rear ends and upper and lower edges. Rivet holes are provided adjacent each end. A cutting portion extends upwardly from the upper edge on the rearward half of the base. A depth gauge extends from the upper edge on the forward half of the base. Said depth gauge terminates at a peak located rearward of the center of the front rivet hole and is spaced from the cutting edge of the cutting portion to provide a gullet. The depth gauge has a leading edge that is inclined rearwardly from the front of the base to the peak. The height of the combined base and cutting portion is no greater than the distance between the centers of the rivet holes plus 10 percent.

Unlted States Patent 1 [in 3,929,049

Graversen Dec. 30, 1975 [54] EXTENDED PITCH SAW CHAIN 3,283,789 11/1966 Silvon 83/834 Inventor: Curtis L. Graversen, Milwaukie, 3,308,859 3/1967 Ehlen 83/834 Oreg' Primary Examiner-Donald R. Schran [73] Assignee: Omark Industries, Inc., Portland,

(mg 57 ABSTRACT [22] Filed: 1975 A cutter link for a saw chain including an elongated 21 L 5 5 150 base having front and rear ends and upper and lower edges. Rivet holes are provided adjacent each end. A Related Apphcanon Dam cutting portion extends upwardly from the upper edge [63] Continuation of Ser. No. 398,143, Sept. 17, 1973, on the rearward half of the base. A depth gauge exabandonedtends from the upper edge on the forward half of the base. Said depth gauge terminates at a peak located U.S-

rearward of the center of the front rivet hole and is [5 Il'rt- Cl. spaced from the cutting edge of the cutting portion to Field Of Search provide a gullet The depth gauge has a leading edge that is inclined rearwardly from the front of the base References C' to the peak. The height of the combined base and cut- UNITED STATES PATENTS ting portion is no greater than the distance between 2,744,548 5/1956 Stephenson et a1 83/834 the centers of the rivet holes P 10 P 2,9l3,023 11/1959 Hazzard 2,924,254 2/1960 Smith 83/834 4 3 Drawmg F'gures US. Patent Dec. 30, 1975 3,929,049

EXTENDED PITCH SAW CHAIN This is a continuation of application United States Ser. No. 398,143, filed Sept. 17, 1973, now abandoned.

This invention relates to an improved saw chain for felling timber and the like and more particularly to a new cutting link configuration.

Saw chain for which the present invention is applicable includes a series of pivotally connected links (pivotally connected by rivets). This series includes center links and side links, the center links having drive tangs and, more commonly, certain of the side links, alternating fron one side to the other, having cutting portions extended opposite from the drive tangs. The cutting portions are of the hooded type, i.e., with a side plate and top plate joined by an integral corner, with the top plate extending over the center links. There is a continuous leading edge formed by the top plate, corner, and adjacent portion of the side plate that is sharpened into a cutting edge.

Whereas improvements have been made in chain saws to enable them to be made smaller, and because of the desirability in the market for smaller, easier handling, less expensive and faster cutting chain saws, saw chain has been required by the chain saw industry to be made smaller. The configuration of the cutting link of the saw chain has been designed over the years largely by trial and error. Thus, the configuration that has come to be standard in the industry is considered most suited for satisfying preference of chip size and clearance, endurance of cutters, ease of sharpening and manufacturing, etc. Thus, as the size of the saw chain was reduced, the configuration of the cutting link was maintained. The pitch of the saw chain is the average distance between the rivets. As pitch increased or decreased, so did all other dimensions. Because pitch is important to match saw chain to drive sprockets, pitch became the term used to measure saw chain size. Thus, whereas a number of years ago a popular sized saw chain for hand chain saws was A inch pitch chain, this was reduced down in stages, e.g. to /s inch pitch chain, /2 inch pitch chain, inch pitch chain and more recently to A inch pitch chain. This reduction in pitch has had a number of effects. A most significant effect is the increased number of parts required for the same length of chain. A foot of 5 1 inch pitch chain includes many more parts than even a inch pitch chain and the cost of making the smaller chains has, accordingly, increased.

It is an object of the present invention to produce smaller size chain while maintaining a larger pitch and fewer saw chain components. It is a further object to increase stability of the chain and greater safety while maintaining or improving cutting efficiency.

Very briefly, in the preferred embodiment of the present invention, the cutting portion of the cutting link is reduced relative (rather than proportional) to the pitch. This reduction reduces the height of the cutting portion which requires reduction in the height of the depth gauge. Thus, for example, the cutting portion is similar to a one-quarter inch pitch chain while all other characteristics (except the depth gauge) simulate a three-eighths inch pitch chain. lt has been found that the reduced cutting portion size and depth gauge height produces a lower profile satisfying the need for smaller size chain and yet because the links are as long as larger chain sizes the number of parts per foot of chain are the same as these larger sized chains.

2 Chip size, chip clearance, power requirements, etc. are the same as obtained by, e.g. conventional one-quarter inch pitch chain.

It will be understood that reducing the cutting por-- tion reduces both its height and length. Previously, a saw chain acceptable to the market required that the cutting portion extend over the maximum length of the base of the link from which the cutting portion and depth gauge extend. Thus the depth gauge was typically extended vertically from the front edge of the base, followed by a gullet (clearance for chips and to permit filing the cutting edge) and the remainder was taken up by the cutting portion. With the reduction in length of the cutting portion (relative to the base), the leading cutting edge can be moved rearwardly on the base and the peak of the depth gauge can similarly be moved rearwardly. The depth gauge can then be inclined rearward and the-inclination of the leading edge produces the very desirable effect of reducing kick back, a recognized hazard in chain saw cutting.

Still further, the lower profile of the cutting portion on the longer base improves the leverage action to inhibit rearing of the cutter (backward pivoting of the cutting link about its rearward most contact with the guide bar) so as: to produce a more stable cutting performance resulting in reduced vibration, reduced wearing of chain saw parts, reduced wearing of the saw chain and smoother, more rapid cutting performance.

Having thus briefly described the preferred embodiment of the present invention and its advantages, a more thorough understanding will be acquired by reference to the following detailed description and drawings wherein:

FIG. 1 is a side view of a length of saw chain incorporating the present invention;

FIG. 2 is a top view of the chain shown in FlG. l; and

FIG. 3 is a side view of the cutting link of the chain shown in FIG. land a conventional cutting link shown in dotted lines overlaying the cutting link of the inventron.

Referring to FIGS. 1 and 2 of the drawings, a length of saw chain incorporating the present invention includes center drive links 10 pivotally interconnected by rivets 12 to pairs of side links. Certain of said side links being tie straps 14 and others being cutting links 16. The cutting links 16 are comprised of a base 18 (corresponding to the configuration of the tie straps 14) from which a cutting portion 20 extends from the rear of the base 18 and a depth gauge portion 22 extends from the front of the baserAs particularly seen from FIG. 2, the cutting portion 20 includes a side plate 20-s and a top plate 20-t. The leading continuous edge of the top plate, corner joining the top plate and side plate, and adjacent portion of the side plate are sharpened to provide a cutting edge 24.

It is to be understood that the reference numerals 18, 20, 22 and 24 of FIG. 1 are applicable to the corresponding parts of the saw chain cutting link illustrated in solid lines in FIG. 3. They have been deleted from FIG. 3 to provide greater clarity. Referring to the dotted overlay of FIG. 3 illustrating a convetional cutting link, the height h is typically greater than the distance d between the rivet holes (center to center) by about 25 percent or more. Hereafter the distance d between centers of the rivet holes in the cutting link is referred to as cutting link pitch. Also reference to the cutting link height refers to the combined height of the base and cutting portion, the lower end of the base being measured from an imaginary line extending along the bottom edge of the tie straps. (When the cutting portion resides on a center link, the portion of the driving tang below the imaginary line is not considered in determining cutting link height.) The length L of the cutting portion (when new) is such as to preferably locate the cutting edge forward of the center line (mid-point between the rivets). The gullet 30 represents the acceptable spacing between the cutting edge and the depth gauge and as will be noted results in locating the peak of the depth gauge (that outermost portion that functions to limit the cutting depth) vertically above the front rivet. The rivets are located as close as practical to the front and rear edges of the cutting link as excessive overhang produces undesired pivoting of these overhanding portions, eg as the chain travels around the ends of the guide bar.

Referring now to the solid line illustration in FIG. 3. Whereas the conventional cutting link height is substantially greater than the cutting link pitch, the improved cutting link of the present invention has a height at least no greater than the cutting link pitch plus percent and preferably no greater than the cutting link pitch. The length L of the cutting portion (in this preferred embodiment) places the leading edge of the cutting portion rearward of the center line c. The peak of the depth gauge portion is rearward of the center of the front rivet hole and preferably rearward of the hole, and the leading edge of the depth gauge is inclined rearwardly from the top front edge of the base to the peak. Thus, the new configuration permits the peak to be located rearward of the front edge of the cutting link by a distance more than half the cutting link pitch whereas the depth gauge of the prior cutting links were substantially less than half this cutting link pitch. With the reduced height of the depth gauge (as measured from the top of the base), the ratio of the height of the depth gauge peak K to the distance it is located rearward of the front edge E is in the order of 2 to 3 while this same ratio on conventional chain, i.e., K to E is in the order of 3 to 2. The degree of incline available is substantially improved and the safety factor for the new chain is thus increased many fold.

Increased stability is also achieved by reason of the reduced moment arm of the cutting force measured as the forces F and F acting against the respective cutting edges creating a pivoting action about pivot P, the rearmost point of the cutting link engaging the guide bar. Thus, the improved chain has greater resistance to rearing back producing greater stability, less vibration, improved wearing, etc.

Having described basically the novel features of the improved saw chain, a specific example of a saw chain incorporating the concepts of the invention is set out below.

EXAMPLE A saw chain of the present invention having a cutting portion simulating a one-quarter inch pitch chain and a base simulating a three-eighths inch pitch was designed as follows:

The cutting link pitch was determined to be 0.390 inch, equal to OREGON 72D brand saw chain having a chain pitch of /3 inch (i.e., inch as an average pitch with the pitch of the drive link being approximately 0.350 inch). The overall length of the cutting link was determined by a determining minimum size aperture or opening for the rivets, and b) providing sufficient material around the rivet opening to satisfy minimum strength and wearing requirements. (The material thickness was 0.042 inch.) For the present chain, the rivet opening was calculated to have a diameter of 0.105 inch and the minimum depth of material around the opening was calculated to be 0.060 inch. It was further determined, however, that the depth of material at each end could be advantageously extended to 0.081 inch and thus the total length was established as 0.390 0.105 2 X 0.081 0.657. The minimum height for the base equals 0.105 inch 2 X 0.060 0.225 inch.

The configuration of the depth gauge was then determined. The height of the chain at the cutting portion above the base equals 0.149 inch (simulating the cutting portion of 4 inch pitch chain). The depth gauge is preferably set 0.025 inch below the cutting edge and thus the height of the depth gauge above the base was calculated to be 0.149 0.025 0.124 inch. The depth gauge length, i.e., from the peak forward to the front edge of the base (with the peak just rearward of the pivot hole), is 0.105 0.081 or 0.186 inch rearward of the front edge of the base leaving adequate room for the gullet and cutting portion. The gullet is 0.175 inch leaving 0.295 for the cutting portion. It will be noted that the height of the depth gauge to its length has a ratio of approximately 2 to 3 to provide for a shallow inclination.

Whereas the preferred embodiment of the invention has been specifically described in the foregoing, it will be understood that numerous variations and modifications will become apparent to those skilled in the art without departing from the invention as defined in the claims appended hereto.

What is claimed is:

1. A saw chain comprised of pivotally connected center drive links and guide bar engaging side links, certain of said guide bar engaging side links being cutting links, said cutting links having a base portion from which is extended a leading depth gauge portion and a cutting portion having a leading cutting edge, said base portion of said cutting links having front and rear rivet receiving openings with rivets therethrough pivotally connecting said cutting links to drive links that precede and follow said cutting links, said base portion further having front and rear bar engaging edge portions and said rear bar engaging edge portion providing at its rearward most point a pivot around which the cutting link pivots as the front end of the cutting link is raised in response to a force acting against the cutting edge, said pivot being located rearwardly of the rear rivet opening and the lengthwise distance between said pivot and the front rivet being substantially greater than the vertical distance of the cutting edge above the pivot, and said pivot located at the rearward most point of the base portion.

2. A saw chain as defined in claim 1 wherein the depth gauge portion of the cutting link has a rearwardly inclined leading edge from a point adjacent to its junction with the base portion to the peak of the depth gauge, said peak being located rearward of the center of the front rivet opening.

3. A saw chain as defined in claim 2 wherein the cutting edge of the cutting portion is located rearward of a vertical line bisecting the distance between the front and rear rivet openings.

4. A saw chain comprised of pivotally connected center drive links and guide bar engaging side links,

certain of said guide bar engaging side links being cutt 6 ward of a plane perpendicular to and bisecting said imaginary line, said depth gauge having its peak located rearward of the front rivet opening and sloping downwardly toward the leading front edge of cutting link and said drive links having front and rear rivet openings spaced apart a distance substantially less than the spacing between the front and rear rivet openings of the cutting links.

UNITED STATES PATENT OFFICE QERTHICATE 0F CORRECTION PATENT NO. 3,929 049 DATED I December 30, 1975 |NVENTOR(5) Curtis L. Graversen it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

CLAIM 4, Col, 5, line 9, after "openings" insert --of--.

line 10, after "links" insert C010 6, line 4, after "0f" insert --said--; and

after "link" insert fiigncd and Sealed this first Day 9? June1976 [SEAL] A nest:

RUTH c. MASON c. mass/mt DANN Altesting Officer Commissioner ujParems and Trademarks Disclaimer 3,929,O49.0u1't2's L. Gmversen, Milwaukie, Oreg. EXTENDED PITCH SAW CHAIN. Patent dated Dec. 30, 1975. Disclaimer filed June 14, 1978, by the assignee, Omaflc Industries, Inc. Hereby enters this disclaimer to claim 1 of said patent.

[Oflicz'al Gazette August 1, 1 978.] 

1. A saw chain comprised of pivotally connected center drive links and guide bar engaging side links, certain of said guide bar engaging side links being cutting links, said cutting links having a base portion from which is extended a leading depth gauge portion and a cutting portion having a leading cutting edge, said base portion of said cutting links having front and rear rivet receiving openings with rivets therethrough pivotally connecting said cutting links to drive links that precede and follow said cutting links, said base portion further having front and rear bar engaging edge portions and said rear bar engaging edge portion providing at its rearward most point a pivot around which the cutting link pivots as the front end of the cutting link is raised in response to a force acting against the cutting edge, said pivot being located rearwardly of the rear rivet opening and the lengthwise distance between said pivot and the front rivet being substantially greater than the vertical distance of the cutting edge above the pivot, and said pivot located at the rearward most point of the base portion.
 2. A saw chain as defined in claim 1 wherein the depth gauge portion of the cutting link has a rearwardly inclined leading edge from a point adjacent to its junction with the base portion to the peak of the depth gauge, said peak being located rearward of the center of the front rivet opening.
 3. A saw chain as defined in claim 2 wherein the cutting edge of the cutting portion is located rearward of a vertical line bisecting the distance between the front and rear rivet openings.
 4. A saw chain comprised of pivotally connected center drive links and guide bar engaging side links, certain of said guide bar engaging side links being cutting links, said cutting links having a base portion from which is extended a leading depth gauge portion and a cutting portion having a leading cutting edge, said base portion of said cutting links having front and rear rivet receiving openings with rivets therethrough pivotally connecting said cutting links to drive links that precede and follow said cutting links, an imaginary line joining the centers of the Front and rear rivet openings said cutting links and said leading cutting edge being rearward of a plane perpendicular to and bisecting said imaginary line, said depth gauge having its peak located rearward of the front rivet opening and sloping downwardly toward the leading front edge of cutting link and said drive links having front and rear rivet openings spaced apart a distance substantially less than the spacing between the front and rear rivet openings of the cutting links. 